The one guide that worked for me was from XboxAchievements, although I found it hard to read;
https://www.xboxachievements.com/forum/topic/238885-memories...The Walkthrough here on TA is incorrect- there's an extra step somewhere in Chisi's Playthrough that throws all kinds of things off making it really difficult to figure out unless you read Japanese (I ended up missing Scene 28 completely, and having no idea how to unlock it while also struggling to find out any information on that particular scene, forcing me to delete my save and restart), so I strongly recommend not using it!
In case the thread gets deleted or XA gets closed or whatever, here's a copy of the guide with some amendments for clarification. By "Arc" they mean "Playthrough", and they start off with Chisa's story as it's the one that gives the most problems;
Arc 1: Chisa Route
- Choice 2
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 2
- Choice 2
Chisa End A
Arc 2: Chisa Route
- Choice 2
- Choice 1
- Choice 1
- Choice 1
- Choice 1
- Choice 2
- Choice 2
- Choice 2
- Choice 2
- Choice 2
- Choice 2
- Choice 1
Save slot 1 (Press X > 3rd Option)
- Choice 2
Chisa End A w/ glasses
Load slot 1 (Main Menu > Continue > Load)
- Choice 1
Chisa End B
Arc 3: Ririsu route
- Choice 1 > All First Decisions > Ending A
Arc 4: Ririsu route
- Choice 1 > All Second Decisions > Ending B
Arc 5: Chloe route
- Choice 3 > All First Decisions > Ending
Arc 6: Suzu route
- Choice 4 > All First Decisions > Ending A
Arc 7: Suzu route
- Choice 4 > All Second Decisions > Ending B
Arc 8: Yuno route
- Choice 5 > All First Decisions > Ending A
Arc 9: Yuno route
- Choice 5 > All Second Decisions > Ending B
Main Menu > Extra Story > Choose Senario > Ending
Scene Title Cleanup:
For scene title cleanup, choose the corresponding scene title, and use the following decision sequences to progress towards 100% scene completion. Sequences are separated by commas.
88: 2
82: 1
81: 3 1 1, 3 2 1, 1 2 1
74: 3
50: 2
46: 2, 3
45: 2, 3
44: 2, 3
43: 2, 3
39: 2
37: 2, 3
36: 2 1, 2 2, 2 3
31: 2 2 3 2
29: 2 (This will say 100% in the scene selection but you must still do this for the completion achievement!)
22: 2 2 2
18: 2 4 1 1 1 1, 2 4 1 2 1 1
After doing all this you can follow the Walkthrough on TA or in the specific achievements to figure out how to unlock them. It's largely just opening the Music, Gallery and Encyclopedia pages and viewing everything.
If the person who wrote the walkthrough ends up amending it to fix his options, I'll happily delete this. Just the trouble I had made this 1-2 hour completion end up taking 6 hours or so, and that's not including the time I spent scouring the internet for answers :)